( 416 ) 
sucked up by this covering and retained through capillarity, so that 
during the flowering- the ovary of Verbascum may be said to be 
covered by a mantle saturated with glucose. 
Tradescantia virginiea L. 
Exactly the same phenomenon of the constant occurrence of a 
clear drop of fluid in the tlower-bud may be observed in Trades¬ 
cantia virginiea. Here the phenomenon is even more striking, because 
there can be no question of the secretion of honey in the Tradescantia- 
flower. Nectaries are not found in the whole order of Commelinacea. 
On sucking up the fluid with a strip of filter-paper and warming 
the paper on the slide with a drop of Ffhling’s solution, we lind 
in this case also, that the fluid does not contain a trace of glucose. 
Just as I pointed out the probability that the drop of water in 
Verbascum is secreted by the hairs with which the stamens are 
covered, so I have reason to believe in the case of Tradescantia , 
that the staminal hairs, so well-known in physiology, secrete fluid 
in their capacity of water-glands. 
Before concluding this communication I consider it necessary to 
explain briefly why the expression “Hydathode” has only been used 
exceptionally. It may be remembered that Haberlandt brings together 
under this expression all “Apparate” and places, where secretion of 
water in the liquid state takes place in the plant, no matter in 
which way the water is set free, whether by active or by passive cells. 
Haberlandt supposed that the whole water-secretion of the plant, 
both at the apex and the teeth of the leaf and superficially by 
external or internal glands, is especially intended to prevent an 
injection of the intercellular spaces, whenever the water which the 
roots take up from the soil has caused an increase of hydrostatic pres¬ 
sure in the vascular bundles; Haberlandt evidently meant to indicate 
by the expression “hydathodes or water-ways” the ways by which 
the excess of water is again got rid of. 
It has been pointed out above that this conception is incorrect and that 
the activity of the internal and external glands is not directly related 
to the bleeding-pressure. The expression could therefore only be retained 
for places of least resistance, which allow the water which the roots 
have pumped up, to pass out when transpiration is impeded; for all other 
places we should, for the sake of clearness, speak of glands. 
For the p laces of least resistance Moll *) has, however, alreadv 
*) J. W., Untersuchungen uber Tropfenausscheidung und Injection bei 
Blattern. Verslagen en Mededeelingen der Koninkl. Akad. v. Wetensch. te Amsterdam 
Dl. XV, 1880. 
